[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 270528
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI NOV 27 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 4N23W 4N38W 4N57W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-6N BETWEEN 20W-25W.
SIMILAR ACTIVITY IS FROM EQ-4N BETWEEN 27W-29W...AND FROM 6N-9N
BETWEEN 26W-30W.

...DISCUSSION...

GULF OF MEXICO...
SURFACE HIGH PRESSURE BUILDS ACROSS THE GULF OF MEXICO TONIGHT IN
THE WAKE OF A COLD FRONT NOW IN THE WRN ATLC AND CARIBBEAN.
THIS AREA OF HIGH PRESSURE ACCOMPANIED BY A COOL AIR MASS IS
ANCHORED BY A 1026 MB HIGH OVER SRN TEXAS. MAINLY NLY WINDS OF 15-20
KT ARE ACROSS THE BASIN REACHING 25 KT IN THE SW AND MIDDLE
GULF...AND 30 KT NEAR THE YUCATAN CHANNEL. IN THE UPPER LEVELS...SW
FLOW COVERS THE AREA AROUND THE NW PERIPHERY OF AN UPPER LEVEL RIDGE
OVER THE CARIBBEAN. MODERATE UPPER LEVEL MOISTURE IS BEING DRAWN
ACROSS THE WRN GULF WITH ASSOCIATED UPPER LEVEL CLOUDS W OF 90W. THE
REMAINDER OF THE BASIN IS UNDER CLEAR SKIES DUE TO MODERATE DRY AIR
AND SUBSIDENCE ALOFT. EXPECT THE HIGH PRESSURE TO SHIFT EWD ACROSS
THE NRN GULF...ALONG WITH CONTINUED STRONG NLY WINDS ACROSS MUCH OF
THE BASIN.

CARIBBEAN SEA...
AS OF 0300 UTC...A COLD FRONT EXTENDS FROM W CUBA TO HONDURAS ALONG
23N80W 19N83W 15N85W. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE
WITHIN 90 NM OF THE FRONT. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS
ARE ALSO AFFECTING ERN NICARAGUA FROM 12N-14N BETWEEN 81W-85W
ASSOCIATED WITH A WEAK DIFFLUENT FLOW ALOFT. BESIDES THE MOISTURE
ASSOCIATED WITH THE FRONT...DRY AIR AND SUBSIDENCE COVERS THE
REMAINDER OF THE CARIBBEAN AROUND AN UPPER LEVEL RIDGE WITH AXIS
NEAR 76W. THIS PATTERN IS PRODUCING GENERALLY FAIR WEATHER ACROSS
THE MAJORITY OF THE BASIN. NW SURFACE WINDS OF 20-25 KT ARE BEHIND
THE FRONT IN THE NW CARIBBEAN. ELSEWHERE...FRESH TO STRONG
TRADEWINDS DOMINATE. EXPECT THE FRONT TO DRIFT E BEFORE STALLING
ACROSS CENTRAL CUBA AND BECOMING DIFFUSE BY EARLY SAT. EXPECT SHOWER
ACTIVITY TO REMAIN ALONG THE FRONT AXIS...AND IN THE SW CARIBBEAN.

ATLANTIC OCEAN...
AS OF 0300 UTC...A COLD FRONT DRAPES ACROSS THE WRN ATLC ENTERING
THE DISCUSSION AREA NEAR 32N71W CONTINUING TO THE NW BAHAMAS NEAR
26N77W TO W CUBA NEAR 23N80W...AND INTO THE CARIBBEAN. SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM AHEAD OF THE FRONT N OF 26N.
ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE ALONG THE REMAINDER OF
THE FRONT. THE FRONT IS SUPPORTED BY AN UPPER LEVEL TROUGH OVER THE
ERN CONUS WITH AXIS ALONG 81W. AN UPPER LEVEL SHORTWAVE RIDGE IS TO
THE E FROM N OF PUERTO RICO ALONG 23N68W TO 40N55W EXTENDING FROM A
LONGWAVE RIDGE OVER THE CARIBBEAN. DIFFLUENT FLOW ALOFT BETWEEN
THESE TWO UPPER LEVEL FEATURES IS ENHANCING THE SHOWER ACTIVITY
AHEAD OF THE COLD FRONT. A WEAK 1016 MB HIGH IS CENTERED NEAR
27N62W. NE OF THE HIGH...A 1013 MB LOW IS CENTERED NEAR 30N58W. A
SURFACE TROUGH EXTENDS FROM THE LOW TO NEAR 25N57W. ISOLATED SHOWERS
ARE TO THE W OF THE LOW N OF 27N BETWEEN 60W-63W. THE LOW IS
SUPPORTED BY AN UPPER LEVEL LOW CENTERED NEAR 29N54W. DIFFLUENT FLOW
ALOFT BETWEEN THIS UPPER LOW AND AN UPPER LEVEL RIDGE WITH AXIS
ALONG 40W IS ENHANCING A LARGE AREA OF SHOWERS/THUNDERSTORMS FROM
12N-28N BETWEEN 43W-49W. A SURFACE TROUGH N OF THE ITCZ EXTENDING
FROM 7N52W TO 15N52W MAY BE INFLUENCING SOME OF THIS SHOWER
ACTIVITY...ESPECIALLY FROM 16N-19N BETWEEN 49W-52W. THE REMAINDER OF
THE ERN ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A
1025 MB HIGH NEAR 29N29W. IN THE UPPER LEVELS...AN UPPER LEVEL
TROUGH COVERS THE ERN ATLC WITH AXIS ALONG 29W. AN UPPER LEVEL JET
ALONG THE ERN SIDE OF THE UPPER TROUGH IS SUPPORTING AN AREA OF
CLOUDINESS/POSSIBLE SHOWERS FROM 15N-24N BETWEEN 15W-27W.

$$
WALTON







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